Seven kids, Taichi, Yamato, Takeru, Sora, Jyou, Koushirou, and Mimi were experiencing strange weather at summer camp. They did not know it at the time, but there was strange weather all over the world. After a snowstorm, they went out and were transported to the Digital World by their Digivices, and they met their partners, Agumon, Gabumon, Patamon, Piyomon, Gomamon, Tentomon, and Palmon, respectively, although they were in their Baby II forms. A Kuwagamon attack, but was driven off when all the Digimon evolved to Child. The kids learned they were Chosen Children, and they encountered several Digimon that had been implanted with Black Gears by Devimon. They freed many Digimon from the Black Gears, and went after Devimon, who absorbed a large number of gears and grew to be gigantic. All the Chosens' Digimon were defeated; however, one, Patamon, who had previously been unable to evolve to Adult, evolved into Angemon. Angemon defeated Devimon, although he used all his energy doing so, and he died.
Takeru, however, recieved Patamon's Digi-Tama, which over time hatched and evolved back into Patamon. Following the battle with Devimon, a man called Gennai appeared and ask the Chosen Children to help him, on the continent of Server. The Chosen Children's friends built them a raft, and the Chosen left File Island. However, they encountered Whamon, who had a Black Gear in him, and he swallowed them. They removed the Black Gear, and he offered to take them to Server. Along the way, they found their Tags, which combined with their Crests would allow their Digimon to evolve into Perfect. First, however, they had to find the Crests.
When they arrived at Server, they encountered Etemon, one of the evil Digimon. They escaped, and eventually all found their Crests. Taichi forced Greymon to evolve to Perfect, and the result was a mistake evolution. Skull Greymon did make Etemon run away, but he was out of control. He devolved, and became afraid of evolving. However, Pixiemon trained them to overcome their fear, and Greymon evolved into Metal Greymon, and defeated Etemon. However, a rift opened, and Agumon and Taichi were blown into the Real World.
Taichi realized he was in the Real World on the same day he left - time in the Digital World ran faster than the Real Worlds time. Taichi went to his apartment, and met his sister, Hikari - and somehow, she knew Taichi. Eventually, Taichi returned to the Digital World, and found the remaining Chosen in disarray. They were all scattered across the Digital World.
All the Chosen were eventually reunited, and they encountered Vamdemon, another Perfect level enemy. Although more of the Chosen were able to evolve their Digimon to Perfect, it was not enough. They infiltrated Vamdemon's castle, but he and many, many of his servants went through a gate to the Real World. The gate closed before the Chosen could follow, but they eventually figured out how to open the gate themselves. They went through with their Digimon, and one by one deleted Vamdemon's servants. They learned he was after an eighth Chosen Child, which turned out to be Hikari, and one of Vamdemon's servant, Tailmon, was her partner. Wizarmon, another of Vamdemon's servants, helped the Chosen, and when Vamdemon attempted to kill Tailmon and Hikari, he jumped in the way and died. All the Chosen's Digimon except Tailmon and Patamon had evolved to Perfect, but it was not enough. Hikari's Crest of Light glowed, and Tailmon evolved into Angewomon, who used everyone's power to delete Vamdemon.
However, Vamdemon had not been completely killed. He returned as Venom Vamdemon, a Final level. None of the Chosens' Digimon were able to defeat him, but they re-read an ancient prophecy Gennai had showed them, and learned how to evolve to Final themselves. Agumon and Gabumon both evolved to War Greymon and Metal Garurumon, both Final levels. Although they were doing well, they could not defeat Venom Vamdemon until everyones Crests glowed and tied him down. At last, Venom Vamdemon was deleted, but the Digital World was completely screwed - it could be seen from the Real World's sky. The Chosen realized they had to return.
Upon their return, the Chosen learned the Dark Masters, Piemon, Mugen Dramon, Pinnochimon, and Metal Seadramon, were the true enemies. The Chosen faced them, and were thoroughly beaten. Later, Pixiemon sacrificed himself to save them again. With Whamon's help, they defeat Metal Seadramon, although Whamon died in the doing. Etemon returned as Metal Etemon, but Zudomon and Saber Leomon were able to defeat him - although Leomon did not survive the encounter. Pinnochimon and Mugen Dramon were defeated by Metal Garurumon and War Greymon, respectively, even though the Chosen were all seperated. Taichi reaized it would take all of them to defeat Piemon, the most powerful of the Dark Masters, and held him off for a while with War Greymon. Once all the Chosen arrived, they, their Digimon, and their Digimon friends began defeating Piemon's army. Angemon evolved into Holy Angemon, and used Heaven's Gate, which Metal Garurumon and War Greymon pushed him in. The Dark Masters were defeated.
Gennai revealed to them that a being had come across the Wall of Fire, a seal between the Dark World and the Digital World. Only enormously powerful Digimon could get through, and that was Apocalymon. Apocalymon's prescence caused the Dark Masters to be born, and through the Digital Worlds time out of sync with the Real Worlds. He was the true and final enemy. The Chosen went against him, and he deleted their Tags and Crests. The Chosen and their Digimon he deleted...
However, in Digital Limbo, the Chosen realized the power to evolve their Digimon was in themselves, and the Crests only represented their abilties. They evolved their Digimon to Perfect and Final, and un-deleted themselves. They managed to defeat Apocalymon, although he attempted to use Grand Death Big Bang, which would have destroyed the Real World and Digital World. The Chosens' Digivices contained the blast, which only served to delete the remaining part of Apocalymon. The Digital World reconfigured, and the Chosen returned to the Digital World, without their Digimon. They did feel that someday they would return, however.